Lock mechanisms using cylindrical keys inserted into an orifice against internal spring pressure and having a plurality of radially disposed projections for actuating corresponding internally radially disposed spring loaded tumblers are highly desirable for maximizing lock security. Such cylindrical key locks have remained relatively difficult to defeat.
However, one disadvantage to cylindrical key locks is that they are very complex and changing the key code combination is extremely costly and difficult relative to more standard flat key locks. In fact, even duplicating a key of an existing cylindrical lock is fairly costly and requires specialized equipment.
Additionally, most existing cylindrical key operated locks require substantial force to both insert the key and subsequently turn the key in order to effect locking and unlocking. Thus, to date, cylindrical key locks have been largely utilized only in high security applications such as safes, alarm systems, and extra heavy duty padlocks. Their use in household doors and for other more common locking applications has been, conversely, avoided.